Contrast of oropharyngeal leak pressure and clinical performance of I-gel™ and LMA ProSeal™ in patients: A meta-analysis

Background Conflicting outcomes have been reported for the i-gel™ and laryngeal mask airway (LMA) ProSeal™ in children and adults during general anesthesia. Randomized controlled trials (RCTs) that yielded wide contrast outcomes between i-gel™ and LMA ProSeal™ were included in this meta-analysis. Methods Two authors independently identified RCTs that compared i-gel™ with LMA ProSeal™ among patients receiving general anesthesia by performing searches in EMBASE, Cochrane, PubMed, and ScienceDirect. Discussion was adopted to resolve disagreements. Data were counted with Review Manger 5.3 and pooled by applying weighted mean difference (MD) and rlsk ratio (RR), and related 95% confidence intervals. Results A total of 33 RCTs with 2605 patients were included in the meta-analysis. I-gel™ provided a considerably lower oropharyngeal leak pressure [weighted average diversity (MD) = -1.53 (-2.89, -0.17), P = 0.03], incidence of blood staining on the supraglottic airway devices [RR = 0.44, (0.28, 0.69), P = 0.0003], sore throat [RR = 0.31 (0.18, 0.52), P<0.0001], and a short insertion time [MD = -5.61 (-7.71, -3.51), P<0.00001] than LMA ProSeal™. Compared with LMA ProSeal™, i-gel™ offered a significantly higher first-insertion success rate [RR = 1.03 (1.00, 1.06), P = 0.03] and ease of insertion [RR = 1.06 (1.01, 1.11), P = 0.03]. The gastric-tube-placement first insertion rate [RR = 1.04 (0.99, 1.10), P = 0.11], laryngospasm [RR = 0.76 (0.17, 3.31), P = 0.72], and cough [RR = 1.30 (0.49, 3.44), P = 0.60] between the two devices were similar. Conclusions Both devices could achieve a good seal to provide adequate ventilation. Compared with the used LMA ProSeal™, the i-gel™ was found to have fewer complications (blood stainning, sore throat) and offers certain advantages (short insertion time, higher first-insertion success rate and ease of insertion) in patients under general anesthesia.


Introduction
The common modality of airway administration in pediatric and adult patients for short surgical operations during general anesthesia is Supraglottic airway device (SAD) [1,2]. Sufficient ventilation, delivery of anesthetic agents and oxygenation are provided with low-risk respiratory adverse events, displacing the demand for traditional tracheal intubation [3]. The secondgeneration SADs with a gastric drain tube have been recommended to decrease the danger of reflux and aspiration of the first-generation tools [4]. I-gel™ and LMA ProSeal™ belong to second-generation SADs.
Given the single-use supraglottic airway, i-gel™ shows a total insertion success rate of 100% with an anatomically designed and noninflatable mask made of a gel-like thermoplastic elastomer; a broadened and flattened stem with a hard bite block is adopted to decrease the axial rotation and malpositioning as a buccal stabilizer, and a port is provided for gastric tube interpolation [5]. The laryngeal mask airway (LMA) ProSeal™ is a laryngeal mask tool with an altered cuff and a drain tube. If inflated, its altered cuff presses the bowl of the tool forwards while improving the seal in virtue of the larynx [6].
To compare the superior airway sealing and certain advantages in patients under general anesthesia between the two SADs, 33 randomized controlled trials (RCTs) that yielded wide contrast outcomes between i-gel™ and LMA ProSeal™ were included in this meta-analysis. OLP was the primary result, and the first insertion success rate, insertion ease, intubation time, gastric-tube first insertion rate, and adverse events related to the SADs were the secondary results. In addition, subgroups analysis were performed in consideration of confounding elements, including age, type of operation, neuromuscular blocker (NMB) application, and the evaluation approach for OLP. "randomized") and "OR" (for "i-gel™" and "i-gel™ laryngeal mask"). The search was performed in English.

Research selection
Only published prospective RCTs that compared i-gel™ with LMA ProSeal™ were included. Case reports, correspondence, reviews, manikin research, animal studies, and non-English articles were excluded.

Data collection
The information below were gathered: the first author's name, year of publication, the number of patients, age, type of operation, NMB application, premedication, mode of ventilation, evaluation approach for OLP, first-insertion success rate, ease of insertion, device insertion time, gastric-tube first-insertion success rate, and adverse events related to the SADs (sore throat, laryngospasm, blood-soiled devices, and cough). The information was collected by two independent authors (Yuan Tan and Jingyao Jiang). Discussion was adopted to resolve disagreements.

Risk of bias evaluation
The risk of bias in RCTs was evaluated by using Cochrane collaboration standards. The criteria were as follows: randomization, concealment of allocation, blinding, incomplete data, selective reporting, and other bias. Each item was judged to be at high, unclear, or low risk of material bias.

Statistical analysis
Data were counted with Review Manger 5.3 and pooled by applying weighted mean difference (MD) and rlsk ratio (RR), and related 95% confidence intervals. The random-effects model was applied if I 2 >50%, which indicated high heterogeneity, and the fixed-effects model was used when I 2 <50%. Possible explanations for great heterogeneity were searched for with a sensitivity analysis. Subgroups were explored in consideration of confounding elements, including age, kind of operation, NMB application, and the promising role of the evaluation approach for OLP. Inspection of funnel plots (if the number of trials was beyond 10) was adopted to test the publication bias of including articles by visually.

Results
Fig 1 illustrates the particular procedures and research selection. The initial search yielded 691 articles (PubMed = 52, Embase = 96, ScienceDirect = 463, Cochrane Library = 80). After excluding duplications, 301 studies were examined. Next, 260 of the 301 studies were excluded because of unrelated studies and reviews. Apart from 1 not retrieved report, the remaining 40 studies were continued to be examined. Then, 7 of 40 studies were excluded based on the exclusion criteria. Finally, a total of 33 studies were included in this meta-analysis [3,[39][40][41]. Tables 1 and 2 show the features and methodological quality of RCTs, respectively.

Discussion
The major finding of the current meta-analysis is that i-gel™ provided a greatly lower OLP, incidence of blood staining on the SADs, sore throat, and a shorter intubation time than LMA ProSeal™ among patients during general anesthesia. In addition, i-gel™ offered a significantly higher first-insertion success rate and ease of insertion than LMA ProSeal™. No great differences were found in gastric-tube placement first-insertion rate, laryngospasm, and cough between i-gel™ and LMA ProSeal™.

PLOS ONE
OLP refers to the airway leak or pressure airway sealing, and it is the most significant index for evaluating the security and effectiveness of airway tools [42]. Between the cuff of the mask and soft tissue around the neck was decided the power of the seal [7,43], the OLP determines the feasibility of the extent of protecting airway and security of positive pressure ventilation. The current meta-analysis observed a greatly higher OLP with LMA ProSeal™ than with i-gel™. The higher OLP in the LMA ProSeal™ group caused by the inflatable cuff with a ventral and dorsal cuff could have led to better seal than i-gel™ with a noninflatable cuff [30]. Growing

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OLP provides specific merits in fat patients, restrictive and obstructive lung diseases, lithotomy position, and pneumo-peritoneum patients [44]. Patient age, the use of NMB, intra-abdominal pressure during operation, evaluation approach of OLP, and LMA size selection standards may influence OLP [45]. Distinct data heterogeneity in the united OLP outcome was observed in our findings. A great heterogeneity (I 2 = 97%) cannot be reduced although different subgroup analyses were adopted, probably due to the application of various sizes of SADs in these trials. The research by Mitra [11] used a 2.5 device. In Shiveshi's research [3], despite the use of 2 and 2.5 devices, the device adopted showed the evident size of 2 in more than 70% of kids. In addition, diversities in induction, maintenance, anesthesia depth, measurement standards, and the number of patients researched might also have contributed to the distinct data heterogeneity.
SADs with an inflatable mask show promise in causing tissue distortion, venous compression, and nerve injury, which translate into the growing incidence of related postoperative morbidity [5]. The incrimination of trauma on insertion, various insertions, and pressure brought by cuff against the pharyngeal mucosa cuff volumes and pressure has been made for postoperative complications [46,47]. In the present study, i-gel™ provided a higher first-insertion success rate, higher ease of insertion, and shorter intubation time than LMA ProSeal™,

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possibly because of a convenient disposable device, relieve of interpolation by stiff bite block, and the natural oropharyngeal curvature of i-gel™ compared with LMA ProSeal™. In addition, we observed that the application of the i-gel™ is related to a lower incidence of pharyngolaryngeal morbidity (blood staining of the SADs and sore throat) compared with the LMA ProSeal™.
By comparing with a previous review [48], our study presented different findings. First, the included studies in the previous review were published from 2009 to 2014, which is a long time ago. However, nearly 50% of the studies [3, 12, 14-16, 22-30, 34, 35, 40, 41] in our present meta-analysis were published after 2014 and reported conflicting results. Second, this work added several new outcomes compared with the past reviews. The first research showed that i-gel™ can offer a higher first-insertion success rate and insertion ease, similar gastric-tube-placement first-insertion rate, laryngospasm, and cough by comparing with LMA ProSeal™ in adults. Third, previous meta-analyses [49] comparing the two devices reported higher a OLP in i-gel™ than LMA ProSeal™ for pediatric patients, forming a contrast against our findings, which indicated that i-gel™ offers a similar OLP compared with LMA ProSeal™ in children. This disparity may be due to the differences in the included studies. Finally, LMA ProSeal™ did not show a higher OLP compared with i-gel™ under conditions of NMB and laparoscopic surgery.
Several limitations were observed in the current work. First, diversities in induction, maintenance, anesthesia depth, and the number of patients researched might have contributed to the distinct data heterogeneity. In spite of subgroups and sensitivity explorations were performed to control several factors, all possible confounding factors cannot be accounted for. Second, while comprehensively searching the published articles, the bias of potential publication might have been present because of the unsuccess to include in-progress or unpublished studies. Third, the mean difference of OLP from the pooled estimates is 1.53, with the absolute value of OLP from the included studies were all more than 20cmH 2 O. An OLP value of more than 20cmH 2 O is generally accepted as an adequate seal. In clinical practice, the difference in OLP values may not be meaningful, when both devices could achieve a enough seal to provide adequate ventilation. In the end, poor quality was found in several included studies. Two studies [24,34] conducted a single-blinded rather than a double-blinded trial, and several research did not illustrate the details of binding in the result evaluation. Hence, extra high-quality research and follow-up studies such as trial sequential analysis are necessary to certify our outcomes.
To conclude, our outcomes showed that both i-gel™ and LMA ProSeal™ may offer a good seal to provide adequate ventilation. In addition, i-gel™ offers certain advantages over LMA ProSeal™ (higher insertion success rate at the first attempt, insertion ease, and rapid intubation time) with limited adverse events (blood staining, and sore throat) in anesthetized patients.